Study On Acid Dissolving Method For The Determination Of Silicon, Chrome And Phosphorus Elements Content In Ferrochromium

The sort of ferrochrome can be classified as micro-carbon, low-carbon, middle-carbon, high-carbon and nitrogen ferrochrome according to the content of carbon. The key of the elements analysis in ferrochrome is digestion of samples. Different decomposable method is fit for different samples. Micro-carbon, low-carbon, middle-carbon ferrochrome can be decomposed with acid solution in which high-carbon and nitrogen-carbon ferrochrome is difficult to dissolve completely. The established analytical method to this kind of sample is using basic fusion for decomposing. This paper studied and established a new method to determine silicon, chrome and phosphorus in high-carbon and nitrogen ferrochrome using acid dissolve for decomposing samples, which is also adapted for another kinds of ferrochrome analysis.In this method, the classic perchloric acid dehydration gravimetric method is changed into molybdenum blue photometric method to quickly determine silicon content. After the samples are dissolved by dilute sulphate, in slight acidic solution, silicic acid and ammonium molybdate take reaction to form into yellow silicomolybdic complex ion, then to use ammonia ferrous sulfate to reduce the formed yellow silicomolybdic complex ion into silicomolybdic blue,of which the strength of the blue is certainly proportional to the content of silicon, consequently silicon content can be determined by photometry.Chrome measurement from ferrochrome is done with wet dissolving method. Orthophosphoric acid is used to decompose samples. Sodium fluoride and K2S2O7 as auxiliary reagent, silver nitrate as catalyzer, oxidized by ammonium persulfate, deacidized by sodium chloride, chrome is titrated by ferrous ammonium sulfate standard solution, with N-phenylated anthranilic acid as a tracer agent.Phosphorus measurement from ferrochrome is done with P-V molybdenum blue photometry. After the sample has been acidulated and dissolved by bromine water and perchloric acid, phosphorus was oxidized into orthophosphoric acid. Chrome was removed from the sample by perchloric acid and hydrochloride, and ferrum can be deacidized by sodium sulfite. After the adding of ammonium molybdate and ammonium vanadate. The P-V molybdenum blue complex can be formed according to the reaction, with the strength was determined by photometry.The acide digestion method for silicon, chrome and phosphorus measurements in high-carbon and nitrogen ferrochrome samples was studied. The kinds of acid, digestion auxiliary reagent and measure method were optimized. The method was proved to have good precision and veracity, which was featured of shorten analytical cycle, rapid measuring speed and high accuracy.